Thread changing devices of embroidering machines serve to carry out changes of color, i.e. to make possible the use of threads of different colors and as the case may be of different kinds one after the other. To this effect known embroidering machines, and in particular small embroidering machines, have as many needle bars as colors to be used, i.e. an independent needle bar with a needle, a thread lever and a thread tightener are available for each different thread and come into operation one after the other. Such solutions are extraordinarily expensive with a view to construction. Moreover, there is a limited number of threads of different colors. In practice the limit of the number of needle bars and thus of the number of colors to be used is between 9 to 10. If more colors and consequently, more needle bars are to be used, the mechanical expenditure, in particular the constructional expenditure, increases, the embroidering head becoming wider. This will in turn strongly restrict the repeat distance from one embroidering head to the neighbouring embroiding head (see leafet of JEMCO CO., LTD., No. 8-6 Kikukawa 1 chome, Sumida-ku, Tokyo, 130, Japan, "HIGH-SPEED AUTOMATIC EMBROIDERING MACHINE").
Further, it has also become known to provide each thread with a thread lever of its own including a thread tightener and a needle of its own, while only one needle bar is available altogether. The latter is displaced laterally for any change of color. The needle then to be used is coupled with the needle bar. The basic problem of limited colors is not solved either (see leaflet Maschinenfabrik Carl Zangs Aktiengesellschaft, D-4150 Krefeld/Federal Republic of Germany, publication no. 172-6 E "Zangs-Multi-Stickronic 172-12 E 172-8 E 172-6 E").
However, it has meanwhile become desirable to use a by far greater number of colors than mentioned before.